High speed data processor line printer

ABSTRACT

A high speed line printer is provided which may be incorporated as a component of an off-line system for printing encoded identification data on labels, or the like. The particular system to be described accepts the output of a data processor, as recorded on a magnetic tape, and it automatically transforms the recorded information into human-readable characters and code bar machine-readable symbols, which are imprinted on labels or other forms. The printer to be described is a drum type, impact, line printer, which is capable of high speed operation, and which is controllable to print out alphanumeric and special characters, as well as a set of code bar symbols for a variety of tag and label sizes, with a high degree of speed, precision and accuracy.

United States Patent 0 [191 Schroeder, Jr. I

[ Mar. 11, 1975 HIGH SPEED DATA PROCESSOR LINE PRINTER [75] Inventor:Marvin C. Schroeder, Jr., Mission Viejo, Calif.

[73] Assignee: Cordura Corporation, Century City,

Calif.

[22] Filed: Aug. 10, 1973 [21] Appl. No.: 387,364

[52] US. Cl. 101/93.21, 197/127 [51] Int. Cl B4lj 1/08 [58] Field ofSearch 101/93 C, 110; 197/127 [56] References Cited UNITED STATESPATENTS 3,185,283 5/1965 Spitsbergen et al 101/93 C X 3,207,067 9/1965Schaller 101/93 C 3,220,343 11/1965 Wasserman 101/93 C 3,406,381 10/1968Peyton 101/93 C X 3,736,868 6/1973 Briggs 101/93 C iliilzi, 6/1973 Combs101/93 c 3,739,719 6/1973 Potter 101/93 C 3,739,720 6/1973 Jones et al.101/93 C Primary Examiner-Edgar S. Burr Assistant Examiner-Edward M.Coven Attorney, Agent, or Firm--Jessup & Beecher [57] ABSTRACT A highspeed line printer is provided which may be incorporated as a componentof an off-line system for printing encoded identification data onlabels, or the like. The particular system to be described accepts theoutput of a data processor, as recorded on a magnetic tape, and itautomatically transforms the recorded information into human-readablecharacters and code bar machine-readable symbols, which are imprinted onlabels or other forms. The printer to be described is a drum type,impact, line printer, which is capable of high speed operation, andwhich is controllable to print out alphanumeric and special characters,as well as a set of code bar symbols for a variety of tag and labelsizes, with a high degree of speed, precision and accuracy.

3 Claims, 16 Drawing Figures DIFFERENTIA I III 5 I00 FLYWHEEL CONTACTROLLER +5VDC TO TRACTOR DRIVE SHAF T AMPLlFlER FMT OHM. l

FMT GHNL 2 FMT CHNL 3 TO CWTROL LER Pmmanm ms I 3.869.980

sum [J1EE 12 TAPE DECK CONTROL PAlhEL CONTROLLER PRINTER INTERFACE UNITPATENTEW sum near 12 PATENTEUMARI H975 9.869.980

SHEET OSUF 12 TOWEL RIBBON RIBBON REVERSING BAR -a4- RIBBON REVERSINGBAR -36- SHEET 08 0F 12 DRUM ROTATION FIG. '9

BAR CODE HIGH SPEED DATA PROCESSOR LINE PRINTER BACKGROUND OF THEINVENTION Line printers are the primary means for making informationavailable for human inspection after it has been processed by electronicdata processing systems. Most present day high speed printers use anon-the-fly printing technique, in which rapidly acting hammers impact acontinuous paper strip against an inked ribbon and a moving typeelement, at the instant at which the selected characters (as representedby the different type elements) are in the appropriate position. Theprint elements of the particular printer with which the presentinvention is concerned are formed on a rotating drum. Speeds of 300-500lines per minute are usual for the prior art on-the-fly line printers.

In a constructed embodiment of the rotating drum on-the-fly printer tobe described, data is printed at a speed of 600 lines per minute, with132 print positions (13.2 inches) per line. The printer in theconstructed embodiment has a standard 96 character set in each printposition, and this includes the human-readable alphanumeric and specialcharacters, and a machinereadable code bar set of numeric and specialcontrol symbols. Because of the line width of 132 positions, a widevariety of tag and label sizes can be printed by the printer of theinvention. The printer to be described may be used, not only forprinting machine-readable code bar identification labels and tags, butalso for usual human-readable alphanumeric printing.

The particular system in which the printer of the invention isincorporated includes a computer-type controller having programmablelogic, and which responds to the input from a magnetic tape, as read bya tape deck which is included as part of the system. The output from thecontroller is interfaced with the printer itself by a suitable interfaceunit, so that the electrical controls of the printer may respond to theinformation recorded on the tape, in order to transform that informationinto appropriate machine-readable symbols, as well as human-readablealphanumeric characters.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective representationof an off-line printing system which incorporates the concepts and:principles of the present invention;

FIG. 2 is a perspective representation of a printer which is included inthe system of FIG. 1 and which is constructed in accordance with theinvention;

FIG. 3 is a schematic representation of a ribbon drive mechanism whichis included in the printer of FIG. 2;

FIG. 4 is a further schematic representation of the ribbon drivemechanism of FIG. 3;

FIG. 5 is a schematic block diagram of a drum drive mechanism which isincluded in the printer of FIG. 2 and which serves to drive the printdrum of FIG. 2;

FIG. 6 is a schematic block diagram of an appropriate electronic systemfor controlling the print cycle and hammer operation of the printer ofFIG. 2;

FIG. 7 is a series of curves useful in explaining the operation of thesystem of FIG. 6;

FIG. 8 is a representation of a print drum which may be incorporatedinto the printer of FIG. 2 in accordance with one embodiment of theinvention;

FIG. 9 is a schematic representation of a column of characters of theprint drum of FIG. 8;

FIG. 10 is a table of characters which may be engraved on the print drumof FIG. 8;

FIG. 11 is a representation of human-readable and machine-readablelabels which may be imprinted by the printer of FIG. 2;

FIG. 12 is a schematic representation of a paper advance mechanismcontained in the printer of FIG. 2 and associated electronic controlcircuitry;

FIG. 13 is a series of curves useful in explaining the operation of thecircuitry of FIG. I2;

FIG. 14 is a functional block diagram of further control circuitry forthe paper advance mechanism of FIG. 12; and

FIGS. 15 and 16 are curves representing waveforms developed in thecircuit of FIG. 14.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT The system shown inFIG. 1 includes a controller 10. The controller 10 may be in the form ofa small computer having programmable logic, and it is operated byappropriate controls mounted on a control panel 12. The controller 10 isalso controlled by information recorded on a magnetic tape which, inturn, is read by the components of a tape deck 14. The informationrecorded on the magnetic tape represents, for example, the output of adata processing system. It is the purpose of the system of F IG. 1 totransform the data processing system output, as recorded on the magnetictape, into appropriate control signals for a printer 16. These controlsignals cause the printer to imprint alphanumeric human-readable data,as well as machine-readable coded symbols, on labels, tags, or otherforms. The controller 10 is coupled to the printer 16 through aninterface unit 18. The purpose of the interface unit is to transform thesignals from the controller into a form acceptable by the controlcircuitry of the printer 16.

The details of the controller 10, the control panel 12, the tape deck14, as well as of the interface unit 18, are known to the art. Thepresent invention is concerned with the construction and electroniccontrol circuitry of the printer 16, which enables the printer to printthe desired machine-readable coded symbols and alphanumeric characterson appropriate forms in an accurate, rapid and precise manner. Asmentioned above, a constructed embodiment of the printer is capable ofprinting at a speed of 600 lines per minute, and of achieving a highdegree of accuracy and precision, and an extremely low rejection rate.

The printer 16 of FIG. 2 may be generally similar to the high speedprinter presently being marketed by Control Data Corporation, RochesterDivision, 1480 North Rochester Rd., Rochester, Mich. 48063, andpresently designated by them as their CL4A8 Series Line Printer andController Equipment. The printer marketed by Control Data Corporationis an electromechanical on-the-fly impact, drum type, line printer. Theprinter 16, as shown in the perspective representation of FIG. 2, issupported in a cabinet which contains compartments for the actualprinter mechanism 20, as well as for an appropriate power supply 22, andother components of a self-contained electronic controller, whichconverts into appropriate printing control signals, the electricalinformation bits received through the interface unit 18 from theexternal controller I0.

The printer mechanism 20 contains the mechanical and electrical systemsrequired to move the paper and ribbon, and to actuate the impacthammers, so as to drivethe paper and ribbon against the print drum atthe proper times to achieve the desired line printing. The printermechanism consists of four main groups, namely, a ribbon drive mechanismand control system, a paper advance mechanism and control system, theprint drum assembly and its associated drive system, and a hammer bankassembly and its associated control system.

The ribbon drive assembly and control system, as shown in FIGS. 3 and 4,includes an alternating current motor 40, two drive clutches 44 and 46,and a ribbon drive control circuit represented by the block 47. A ribbon30, shaped as a continuous towel, is looped around an upper ribbon roll32, over an upper reversing bar 36, and around a lower ribbon roller 38.The ribbon 30, for example, may be inches wide and 25 feet long, and itmay be formed of nylon, Mylar, or other suitable material.

The drive motor 40 runs continuously whenever the printer is energized.The ribbon drive control circuit 47 is used to provide control signalsto the clutches 44 and 46. When the clutch 44 is energized, the roller32 rotates to drive the ribbon in one direction, and when the clutch 46is energized, the roller 38 rotates to drive the ribbon in the oppositedirection. The control circuit 47 responds to an appropriate ribbonadvance command signal from the controller to cause one of the clutches44 and 46 to be engaged with a high current so as to drive the ribbon ina particular direction. At the same time, the other clutch is energizedwith a low current so as to act as a drag on the ribbon and therebymaintain the ribbon in a taut condition.

The ribbon advance command signal is active at the beginning of eachprint operation, and it remains active throughout the print operation.Upon the termination of the ribbon advance command signal, the controlcircuit 47 keeps the clutches engaged for a half second after the printoperation, to move the ribbon into position for the next printoperation. The direction of the ribbon feed is controlled by a flip-flopin the control circuit 47 which, in turn, is operated by limit switchesin the ribbon drive mechanism. This flip-flop determines which of thetwo clutches 44 and 46 is to be energized at a high current level tomove the ribbon in a particular direction, and which is to be energizedat a low current to provide the desired drag on the ribbon.

The print drum assembly and associated control circuitry are shown inFIGS. 5 and 6. The print drum is designated 50 in FIG. 5. As will bedescribed in more detail subsequently, the print characters are engravedon the drum in horizontal rows of like characters. As each row ofcharacters rotates into a printing position, upon rotation of the printdrum, the print hammers are actuated in the column positions at whichcharacters are to be printed. The print drum 50 is driven by an electricmotor 56 through a belt drive 58, The motor causes the drum to rotatecontinuously whenever power is supplied to the printer.

As shown in FIGS. 5 and 6, a toothed character index timing wheel 52 isaffixed to one end of the print drum 50. The timing wheel 52 has teethcorresponding onefor-one with each drum row character, and it also has ablank tooth index position corresponding to a blank character row on thedrum. The teeth of the timing wheel 52 are sensed by a magnetic pick-up54 which introduces a series of electric pulses to the circuit of FIG.6, as the print drum rotates. These input pulses cause the circuit ofFIG. 6 to generate corresponding output pulses which are applied to acharacter counter in the controller so as to control the print cycle.The character counter generates a code signal for each angular printposition of the print drum. The code signal corresponds to theparticular character engraved on the drum at that print position. Printhammers at each column position identified by the controller by acorresponding code are then actuated.

As shown in FIG. 6, the output of the magnetic pickup 54 is introducedto a level detector 55 and to a differential amplifier 57. The pick-upis shunted by a capacitor CO3 which function as a low pass filter. Theoutput of the level detector is connected to a capacitor CO4 which alsoserves as a low pass filter, and through an inverter II to a flip-flop0R1, 0R2. The output of the differential amplifier 57 is connected tothe input of a character phasing one-shot multivibrator 59, the outputof which is connected to a second one-shot multivibrator 61. The outputof the multivibrator 61 is connected through an inverter I3 to a firstoutput terminal which develops drum row pulses for the controller, andthrough a second inverter 14 to an output terminal which develops enablepulses for the hammer drive mechanism.

The various waveforms developed within the circuit of FIG. 6 are shownin FIG. 7. The purpose of the circuit of FIG. 6 is to develop a DRPpulse for each line position of the print drum, as well as a HEP pulsefor each angular position. The DRP pulses are used by the controller toadvance the character counter and to set up a print cycle, as describedabove. The HEP pulses are used by the hammer control mechanism to enablethe hammers to actuation at the proper times. As shown by the waveformsof FIG. 7, the pick-up signal generated by the sensor 54 has a generallysine wave form, and is generated as each gear tooth of the timing wheel52 passes the magnetic reluctance pickup The level detector 53 is madeconductive when the sine wave signal swings in a positive direction, andit remains conductive until the negative swing of the sine wave signalpasses the 1 .volt level.

The flip-flop 0R1, 0R2 is set, therefore, only during the negative swingof the sine wave signal. As the sine wave signal swings positive, thedifferential amplifier 57 is made conductive, and it serves to reset theflipflop. Thus the flip-flop will remain reset during the positiveportion of the sine wave signal, and it will be set during the negativeportion. The character phasing one-shot multivibrator is triggered eachtime the flipflop resets. The length of the output pulse from theone-shot is adjustable through a phasing control knob mounted on thecontrol panel. As the character phasing pulse drops to zero, the oneshot61 is triggered. The output from the flip-flop is, for example, a 50microsecond pulse which is introduced to the two inverte r s togvelopthe DBP and HEP outputs. As mentioned above, the hammer controlmechani'sTn utilizes the HEP output to cause the impact hammers to beoperated at the proper time.

The drum 50 shown in FIG. 8, in a particular embodiment of theinvention, has a diameter of 4.890 inches, and it is 136 columns inlength. The illustrated drum, for example, has 96 character rows spacedaround its periphery. Eighteen bar code symbols are displayed in thefirst 36 rows, as shown in FIG. 9, and as listed in the table of FIG.10. The bar code symbols are arranged in a checkerboard manner on thedrum, in that the same symbols appear, in each instance, in two adjacentrows, with the symbols appearing in the odd numbered columns in oneofthe rows, and in the even numbered columns in the other of the rows,such as shown in FIG. 8. An alphanumeric character, such as a may bepositioned in the otherwise vacant positions between the checkerboardbar code symbols, as shown in FIG. 8. The checkerboard design is carriedthroughout the 36 bar code sequence in rows 1-36. All the otheralphanumeric and special characters are displayed in all 136 columnpositions across their respective rows. The reason for the cheeckerboardarrangement of the code bars is to prevent shadowing, in that when thecode bars are closely adjacent to one another, the print hammers have atendency to move the ribbon against an adjacent symbol which has notbeen selected for printing.

When the printer is commanded to print a bar code, the program in thecontroller determines which column and row is to be impacted by theprint hammers and, if a full row of bar code zeros, for example, were tobe printed, the controller would cause the printer to fire selected oddcolumns in row 35 and selected even columns in row 36, thereby printinga full line of bar code zeros adjacent to one another and withoutshadowing. In the case of the alphanumeric and special characters, thetendency for shadowing does not occur, and the program in the controllercauses such characters to be printed in any column for which they areselected.

The purpose of the bar code symbols is to permit items identifiedthereby to be read automatically by a hand held wand. The wand iselectrically connected to appropriate apparatus, so that signalsgenerated by the wand as it is swept across an imprinted bar code symbolare received and sensed by the apparatus. The symbols, for example, maybe affixed to merchandise, and the wand may be held by a check-outclerk, automatically to control the cash register.

To print readable bar code symbols of sufficient height to be read by ahand-held wand, which should have a heighth of at least 0.260 inches, ina high speed line printer which has hammer faces of the order of 0.150inches in height, and characters of the order of 0.100 inches in height,it is necessary to move the paper a small enough increment during thebar code symbol printing to allow for an over-printing technique to beemployed so that a continuous vertical line can be printed on the paperfor each element of the individual bar code symbols. The normal verticalpaper movement spacing of six or eight lines per inch, which is standardin conventional high speed line printers, will not provide theappropriate paper control for the printing of the bar code symbols.Therefore, some means must be provided for controlling the papermovement to something less than 0.100 inches.

In the apparatus of the present invention, a disc encoder is used tocontrol the vertical movement of the paper. The disc encoder producesoutput control pulses, each of which corresponds, ina constructedembodiment, to 0.02003 inches of paper movement. Therefore, by selectingthe proper number of pulses from the encoder for any desired program,virtually any desired paper movement can be achieved.

The drum 50 in a constructed embodiment rotates at 600 rpm, or 100milliseconds for each complete revolution. It takes one character block(0.1598 inches) 1.0416 milliseconds to pass any given point. The papermovement time is controlled to be 25 milliseconds for a single spaceadvance. However, to print the bar code symbols, three space advancesare used for each symbol, and the printing time is then 41.8milliseconds for each three space moves.

In the operation of the printer, and as shown in FIG. 11, allalphanumeric and special characters are printed on the first line of theform, or label; up to nine spaces are moved from the first line printedto the first bar code line; the bar code is printed in three strikes,overlapping approximately 0.020 inches; the printer than moves one spaceto the last line to be printed which comprises all numerics, allunderlined numerics, and certain special characters. Then, as shown inFIG. 11, the printer moves two spaces to the first line location on thesucceeding form, and will wait for the first character in thealphanumeric section of the drum to be in print position.

When the sequence shown in FIGS. 8, 9 and 10 is used for imprintingforms of the type shown in FIG. 11, a time saving is achieved in thatthe print drum in each instance is in proper position to proceed fromthe alphanumeric line to the bar code line and from the bar code line tothe numeric line on the label with a mini mum of rotational movement ofthe print drum.

After each line of the form of FIG. 11 is printed, proper spacing occursin accordance with a received vertical format instruction. The verticalformat instructions are derived from a vertical format tape assembly, tobe described, as well as from encoder signals derived from an encoder,which will also be described. The vertical format tape signals are usedto move the paper from one form to the next, and the encoder signals areused to space the printer to the various lines within the individualforms themselves. To obtain a full format tape capability, a six oreight line option is used in the constructed embodiment, and the formattape is punched to match the six or eight line per inch spacing mode, asselected by the operator.

The paper transport mechanism, and associated cir cuitry, as shown inFIG. 12, includes a flywheel which is coupled to a drive motor through abelt 102. The drive motor rotates the flywheel at a constant speed aslong as main power is supplied to the printer. The flywheel shaft iscoupled to a clutch and brake assembly designated 104 and 106. A paperadvance signal causes the clutch 104 to engage the drive shaft at thesame time the brake 106 releases, causing the paper to advance. A pairof toothed pulse wheels 112 and 114 are keyed to the shaft 110, andthese wheels contain teeth spaced to correspond respectively to six andeight inches per length formatting. A correspond ing pair ofelectromagnetic reluctance pick-ups 116 and 118 are associated with therespective wheels 112 and 114, and these pick-ups introduce pulses to alogic control circuit 120.

The drive shaft 110 is also coupled through a belt 124 to a drivesprocket 126 of a format tape system 128. The format tape system 128includes a format tape 130 which extends around an idler roller 132,around the drive sprocket 126 and around a further roller 134. Anencoder is also coupled to the drive shaft. This encoder may be of thetype presently marketed by Disc Instruments, Inc. of 2701 South HalladaySt., Santa Ana, Cal. 92705, and designated by them as their Rotaswitchincremental shaft encoder, Model 832-144- 18-1BLP. The drive shaft 110also drives a belt 136, which is connected to the tractor driven shaftof the paper advance mechanism.

As shown in FIG. 12, the pick-up 116 is connected to a differentialamplifier 150 and to a level detector 152 in the circuit 120, whereasthe pick-up 118 is connected to a differential amplifier 154 and to alevel detector 156. The level detector 152 is connected through aninverter to the set input terminal of a flip-flop 158, 160; whereas thedifferential amplifier 150 is connected to the reset input terminal. Thereset output terminal of the flip-flop is connected through an and gate162 to the input of a one-shot multivibrator 164.

Likewise, the level detector 156 is connected through an inverter 166 tothe set input terminal of a flip-flop 168, 170. The differentialamplifier 154 is connected to the reset input terminal of the flip-flop.The reset output terminal of the flipflop is connected to an and gate172, the output of which is connected to the one-shot multivibrator 164.A switch 179 is provided on the control panel, which is operated by theoperator to select either a six line per inch or an eight line per inchformat. When the eight line per inch format is selected, the and gate162 is enabled, and when the six line format is selected, the and gate172 is enabled.

The output of the one-shot 164 is introduced to an and gate 180. Theoutput of the encoder 135 is introduced to an and gate 182. The and"gates 180 and 182 are connected through an or gate 184 to the outputterminal 186 of the circuit. A VFU command signal is applied to the and"gate 180, and its complement is applied to the and gate 182. The VFUcommand signal when true, causes the output from the circuit 120 to beapplied to the controller. However, when the complement of the commandsignal (VFU) is true, the output of the encoder 135 is applied to thecontroller.

The format drive assembly 128 includes a brush reader unit containing aplurality of metal brushes 140 which sense holes in the various channelsof the format tape 130, as selected by the controller. A strobed stopsignal is allowed to take effect when a hole in the format tape enablesa brush to strike the metal contact roller 134. When the VFU commandsignal is true, the format assembly determines when the pulse will begenerated which will disengage the clutch 104 and engage the brake 106to stop the paper movement.

However, when the complement of the command signal VFU (VFU) is true,the encoder 135 determines when a pulse will be generated that willdisengage the clutch 104 and engage the brake 106 to stop papermovement. When the term VFU is true, the pulse from the format controlsystem determines which of the pulses from the pick-up 116 or from thepick-up 118 will be used to stop the pa er advance mechanism. On theother hand, when the signal is true, the pulses from the encoder 135will determine when the paper advance mechanism is to be stopped. Thevarious waveforms generated within the system of FIG. 12 are representedby the curves of FIG. 13.

Therefore, the sequence is such in the printing of a form, such as shownin FIG. 11, for example, that a paper advance signal is received fromthe controller to advance the paper to the first line of the form. Uponreceipt of the paper advance signal, the brake 106 releases and theclutch 104 engages, as described above, so that the drive shaft 110drives the paper and associated controls to the first line. At thattime, the W signal is true, and the first line is designated by thefirst pulse from the encoder 135. The printer then prints thealphanumeric characters on the first line of the form.

When the printing operation is completed, the controller againintroduces four pulses of the paper advance signal to the mechanism, andthe paper'advances a desired distance, still under the control of theencoder 135. The first portion of the bar code signals are then printed.Then, the controller introduces two pulses of the advance signal to themechanism, and under the control of the encoder 135, and the paperadvances a further desired amount, and the next portion of each bar codecharacter is printed. The operation is repeated, still under the controlof the encoder 135, and the paper advances another two pulse distance sothat the third portion of each bar code character may be printed.

The next operation is for the controller to advance the paper atwo-pulse distance to the last line of the form, in which the numericsymbols are printed. The VFU signal now becomes true, so that thecontrol of the paper advance mechanism is switched to the form atcontrol system 128. The paper is then advanced a further two-pulsedistance to the first line of the next form, at which position the paperis stopped, under the control of the signal from the format tape system28.

When the sequence shown in FIGS. 8-10 is used for engraving the varioussymbols and characters on the drum, the drum rotation is minimized,because the angular position of the drum at the end of each printoperation is such that the angular displacement for the next charactersis minimized. This sequence arrangement optimizes the speed at which theprinting operation can be carried out.

Therefore, control of the vertical line spacing is accomplished by theholes punched in the format tape of the format tape system 128, and bythe pulses derived from the encoder 135. The format tape itself isformed into a loop, and it is punched at six and eight lines per inchsegments in the particular embodiment. As each frame passes the readstation, a stop pulse is generated by the pick-ups 116 or 118, and theparticular stop pulse which occurs coincidentally with the sensing of ahole in the format tape is supplied to the controller, for the purposedescribed above. Asalso described, the

two reluctance pick-ups 116 and 1 18 sense the position I of therespective timing wheels 112 and 114 for generating the stop pulses.Both pick-ups drive identical pulse shaping circuits in the circuit 120,as described. Each pulse shaping circuit is composed of a common basedifferential amplifier, voltage level detector, and an RS flip-flop. Theline select switch 179 located on the control panel permits the operatorto select either the six or eight LPI-shaped signal to trigger theoneshot 164 to generate the STP pulse.

As described above, the vertical movement of the forms of FIG. 11through the printer, and the resulting spacing from one print line tothe next, is controlled by alternately energizing a magnetic clutch 104and a brake 106, which transmit torque from the drive motor to the formsdrive tractor and to the vertical format brush reader 128. The circuitswhich drive the clutch and brake receive their inputs from the printercontrol- Ier, as also described above. The controller acts upon advancecommands received from the data source. The controller monitors theoutput of the vertical format tape reader 128, and of the logiccircuitry of FIG. 12, to determine when each form has reached aspecified number of line spaces for a print operation to be initiated.The controller then commands the clutch/brake circuits to start and stopthe motion of the forms, as described.

The motion of the forms through the printer is controlled by the advancesignal from the controller, as described. When the advance signal is atlogic 1, the forms move through the printer, but when the bar advancesignal is at logic 1, the motion of the forms is stopped. The forms aredriven when the advance signal goes to a logic 1 level and continueuntil the bar advance signal goes to a logic 1 level. If the bar advancesignal remains at a zero level for more than 1.35 seconds, a flip-flop200 in FIG. 14 is set to indicate a paper runaway condition. Under thislatter condition, the motion of the forms is automatically terminated toprevent unwanted slewing of the forms.

In the circuit of FIG. 14, the advance signal from the controller ispassed through an inverter circuit 202 to an and gate 204. The output ofthe inverter is also applied through a delay network 206 to the setinput of the runaway flip-flop 208. The flip-flop 208 is reset by amaster clear input received from the controller. The reset output of theflip-flop 208 is applied to the and" gate 204. The output from the andgate is applied through an inverter 210 to a one-shot multivibrator 212,and through a second inverter 214 to a oneshot multivibrator 216.

The output from the converter 214 is applied through a clutch drivertransitorized circuit 215 to a hold coil in the clutch 104; whereas theoutput from the one-shot 216 is applied through the circuit 215 to adrive coil of the clutch 104. Likewise, the output from the inverter 210is applied through a transistorized driver circuit 217 to a hold coil ofthe brake 106, whereas the output from the one-shot 212 is appliedthrough the driver circuit 217 to a hold coil in the brake. The variouswaveforms appearing throughout the circuit of FIG. 14 for a single lineadvance are shown in FIG. 15, and for a multi-line advance are shown inFIG. 16.

The clutch 104 and the brake 106 each have two modes of operation,namely drive" and hold. For clutch drive, a high current is applied tothe low resistance clutch coil for six to eight milliseconds duration tocause rapid acceleration of the tractor drive shaft. The clutch drive isturned on by a -1 transition of the ADV signal. At the same time, a lowcurrent is applied to the high resistance hold coil of the clutch tosustain tractor shaft velocity following initial acceleration from adead stop. The hold current remains on until a specified number of lineshave been moved.

A high current is applied to the low resistance brake drive coil of sixto eight milliseconds duration to cause rapid deceleration of thetractor drive shaft when the ADV signal changes from 1 to 0. At the sametime, a low current is applied to the high resistance brake hold coil toprevent motion of form while the printer is idle, or printing a line ofdata. Brake hold current is applied as soon as the power is turned on,and also by the 1-0' transition of the ADV signal.

As shown in the diagram of FIG. 1, the ADV fed to the circuit is firstinverted by the inverter 202. The inverter output is "anded with thepaper runaway output from the flip-flop 208, and is inverted again bythe inverter 210. In addition, the inverter 202 drives a 1.35

second RC time delay circuit. If the output from the inverter 202remains at logic 1 level for 1.35 seconds, the delay dircuit generates alogic 1 at its output which sets the paper runaway flip-flop 208. Withthe flip-flop 208 set, the and gate 204 is disabled, and the resultingoutput from the inverter 210 activates the brake and disengages theclutch.

A single line advance as shown in FIG. 15 is initiated when thecontroller drops the ADV signal to a logic 0 level. This causes thebrake hold current to turn off and the clutch hold and drive currents toflow through the clutch coils. For a single line advance, the first STPpulse from the s stem of FIG. 12 causes the controller to switch the ADsignal back to logic I, turning off the clutch hold and turning on thebrake hold, and triggering the one-shot 212. Hence, the brake hold anddrive currents are turned on. The brake drive current turns off aftersix to eight milliseconds. However, the brake hold current remains onuntil the next form advance command is received.

For a multi-line advance, the controller switches the ADV signal back tologic 1 (as shown in FIG. 16) after more than one STP pulse is sensed bythe system of FIG. 12; that is, two pulses for two line advance, threepulses for three line advance, and so on. The clutch hold currentremains turned on until the specified number of lines have moved, andthen the above-described braking operations are initiated.

The invention provides, therefore, an improved high speed data processorline printer, which is capable of accurately and quickly printing barcodes on labels, or other forms, in a simple, precise andstraightforward manner, and in a minimum of time. While a particularembodiment of the invention has been shown and described, modificationsmay be made. It is intended in the claims to cover the modificationswhich fall within the spirit and scope of the invention.

What is claimed is:

1. In a high speed line printer system which includes a frame; a printdrum rotatably mounted on said frame and having a plurality of differentbar code symbols engraved on the peripheral surface thereof in aplurality of different longitudinal rows angularly spaced around theperiphery from one another, and with each row containing identical barcode symbols; a paper drive mechanism mounted on said frame for movingforms on a line-to-line basis past said print drum to be imprinted bysaid bar code symbols; impact hammer means mounted on said frame;control circuitry coupled to said impact hammer means for causing saidimpact hammer means to drive said forms against the bar code symbols onsaid print drum at controlled times; electrical signal generating meanscoupled to said paper advance mechanism for producing electric pulsesrepresentative of each line advance of said paper drive mechanism withrespect to a first predetermined line per inch reference standard; aformat control system mechanically coupled to said paper drive mechanismand to said generating means for generating electrical control signalsindicative of advances of said forms by said paper drive mechanismthrough predetermined numbers of lines; the combination of an encodermechanically coupled to said paper advance mechanism for generating anelectric signal representative of each line of advance of said paperdrive mechanism with respect to a second predetermined line per inchreference standard; logic circuitry electrically con nected to saidformat control system and to said encoder for generating electric outputsignals selectively representative of the electrical control signalsfrom said format control system and of said electric signal from saidencoder; and control means coupled to said paper drive system andresponsive to the output signals from said logic circuitry to stop thepaper drive system at predetermined positions of the forms under thecontrol of the format control system during one operating mode and underthe control of the encoder during a second operating mode.

2. The high speed line printer system defined in claim 1, in which saidcontrol means responds to signals from ing mode to cause each of saidbar code symbols to be imprinted in an overlapping manner during each ofa plurality of successive print operations.

* k i i

1. In a high speed line printer system which includes a frame; a printdrum rotatably mounted on said frame and having a plurality of differentbar code symbols engraved on the peripheral surface thereof in aplurality of different longitudinal rows angularly spaced around theperiphery from one another, and with each row containing identical barcode symbols; a paper drive mechanism mounted on said frame for movingforms on a line-to-line basis past said print drum to be imprinted bysaid bar code symbols; impact hammer means mounted on said frame;control circuitry coupled to said impact hammer means for causing saidimpact hammer means to drive said forms agaInst the bar code symbols onsaid print drum at controlled times; electrical signal generating meanscoupled to said paper advance mechanism for producing electric pulsesrepresentative of each line advance of said paper drive mechanism withrespect to a first predetermined line per inch reference standard; aformat control system mechanically coupled to said paper drive mechanismand to said generating means for generating electrical control signalsindicative of advances of said forms by said paper drive mechanismthrough predetermined numbers of lines; the combination of an encodermechanically coupled to said paper advance mechanism for generating anelectric signal representative of each line of advance of said paperdrive mechanism with respect to a second predetermined line per inchreference standard; logic circuitry electrically connected to saidformat control system and to said encoder for generating electric outputsignals selectively representative of the electrical control signalsfrom said format control system and of said electric signal from saidencoder; and control means coupled to said paper drive system andresponsive to the output signals from said logic circuitry to stop thepaper drive system at predetermined positions of the forms under thecontrol of the format control system during one operating mode and underthe control of the encoder during a second operating mode.
 1. In a highspeed line printer system which includes a frame; a print drum rotatablymounted on said frame and having a plurality of different bar codesymbols engraved on the peripheral surface thereof in a plurality ofdifferent longitudinal rows angularly spaced around the periphery fromone another, and with each row containing identical bar code symbols; apaper drive mechanism mounted on said frame for moving forms on aline-to-line basis past said print drum to be imprinted by said bar codesymbols; impact hammer means mounted on said frame; control circuitrycoupled to said impact hammer means for causing said impact hammer meansto drive said forms agaInst the bar code symbols on said print drum atcontrolled times; electrical signal generating means coupled to saidpaper advance mechanism for producing electric pulses representative ofeach line advance of said paper drive mechanism with respect to a firstpredetermined line per inch reference standard; a format control systemmechanically coupled to said paper drive mechanism and to saidgenerating means for generating electrical control signals indicative ofadvances of said forms by said paper drive mechanism throughpredetermined numbers of lines; the combination of an encodermechanically coupled to said paper advance mechanism for generating anelectric signal representative of each line of advance of said paperdrive mechanism with respect to a second predetermined line per inchreference standard; logic circuitry electrically connected to saidformat control system and to said encoder for generating electric outputsignals selectively representative of the electrical control signalsfrom said format control system and of said electric signal from saidencoder; and control means coupled to said paper drive system andresponsive to the output signals from said logic circuitry to stop thepaper drive system at predetermined positions of the forms under thecontrol of the format control system during one operating mode and underthe control of the encoder during a second operating mode.
 2. The highspeed line printer system defined in claim 1, in which said controlmeans responds to signals from said logic circuitry during the firstoperating mode to move the paper drive mechanism from one form to thenext, and in which said control means responds to the output signalsfrom said logic circuitry during the second operating mode to move thepaper drive mechanism to selected lines within the individual forms.